Integrally geared compressors are used to compress air or chemical gases, for air separation, in metallurgy and in other processes. The air or other gases, which are likewise referred to as air below for the sake of simplicity, is compressed to a first pressure in the first process stage and then fed to the second process stage, where it is compressed to a second, higher pressure.
Large integrally geared compressors, e.g. those for modern air separation plants for the production of several thousand tonnes of oxygen per day, must compress high volume flows with a high efficiency. To achieve a high efficiency, the process stages effecting the air compression are operated at different rotational speeds, wherein the second process stage is generally operated at a higher rotational speed than the first process stage.
To produce the different rotational speed with a single compressor drive, the integrally geared compressor is equipped with a gear, which couples the two process stages to each other with different rotational speeds. The drive can be either an electric motor or a turbomachine, e.g. a steam turbine or a gas turbine.
A device of the type in question is already known from the following documents: US 2007/134111 A1, U.S. Pat. No. 4,105,372 A, EP 0 653 566 A1, U.S. Pat. No. 4,047,848 A.